Apparatus for making small castings



Aug. 6, 1929. P. A. PITMAN 1,723,071

APPARATUS FOR MAKTNG SMALL CASTINGS Filed Aug. 6, 1926 Patented ug. 6, 1929.

UNITED STATES PAUL A. PITMAN, OF QUINCY, MASSACHUSETTS.

APPARATUS FOR MAKING- SMALL CASTINGS.

Application led August 6, 1926.

This invention .ates to apparatus for making castings by the use of fluid pressure to force the molten metal from the Crucible into the mold.

in the casting of objects by this method, aarticularly objects made of gold, silver and platinum, a vital factor is the time interval between the heating period and the application of Huid at a working pressure sufficient to force the metal into the mold. For example, in making small dental castings an interval of one half second in applying the working` pressure to the molten metal may defeat the casting, whereas, if the interval were reduced to one fifth of a second the resuit would be satisfactory. l

TDental and other small castings have been made by the use of apparatus comprising a stationary tank or reservoir containing air or nitrous oxide gas under pressure, a flexible pipe from one to two feet long for connecting the tank and the flask of the mold, and a valve operated by movement of the flask r the pipe-coupling to release the fluid stored in the tank so that it may fiow through the flexible pipe to the flask. The area of the connecting passageway formed by the flexible pipe, the elasticity of the rubber or other material of which the flexible pipe is made, and the distance to be traveled by the fluid from the tank to the crucible retard the development of pressure in the latter so long that very small bodies of molten metal lose their fluidity during the interval above inen tioned.

ln view of these conditions an object of the present invention is to provide improvements in casting apparatus by which the aforesaid interval may be substantially sliertened, to the end that even the smallest practicable castings, for example, dental inlays, may be made.

To accomplish this result my invention provides the novel combination comprising a tank or reservoir for the operating fluid, a releasing valve in the discharge port of the reservoir, a coupling device attached directly to the reservoir and movable relatively thereto, and means operable by relative movement of the coupling device and the reservoir to open the valve. This combination eliminates the usual flexible pipe and so shortens the distance and otherwise reduces the area of the passageway from the source of supply to the Crucible that an apparatus embodying this feature will operate satisfactorily under con- Serial No. 127,592.

ditions that cause prior devices for the same purpose to fall.

Another novel feature consists n. an iinl proved organization comprising a tank or reservoir and means for to the flask. A

The invention also includes an improved coupling device, and other novel features hereinafter described and claimed and illustrated by the accompanying drawings.

Referring to the drauf'inga- Y 1 is an elevation of a casting apparal tus embodying a preferred form of the inveir tion;

Fig. 2 is a vertical section including a portion of the base, a portion of the .fluid-reservoir, the coupling device, and broken lines representing a flask in operative position;

Fig. 3 is a cross-section on line 3-3 of Fig. 2;

Fig. l is a perspective view of a preferred type of releasing valve;

Fig. 5 is a horizontal section on line 5--5 of Fig. 1; and

Figs. 6, 7 and 8 are sectional views of flasks of various sizes in which molds have been formed.

The illustrated apparatus comprises a frame having a base 10, a gooseneck 11 and a vertical sleeve or bearing 12 for the fluidreservoir 13. The latter is cylindric and is adapted to slide up and down in the bearing 12. it is supported by a friction device shown in Fig. 5 and consistingof a leaf spring 14. This spring is a normally flat strip of steel flexed and seated in an internal groove 15 formed in the bearing 12. lts inid-port`ion bears on the reservoir with suliicient pressure to sustain the latter and all the other elcments carried thereby.

The reservoir is provided with a handle 16, a pump 17 and a pressure 18. The barrel of the pump is preferably nested in the reservoir for the sake of compactness and extends through the handle 16. The pump plunger projects from the upper end of the barrel and is provided with a handle 19. The discharge end of the pump is in the reservoir and at the lower end of the barrel. By virtue of this construction the reservoir, the pump and the pressure gage form a movable unit.

The base 10, as shown, is formed with three seats 20, 21 and 22 for three sizes of flasks, and with a hole 23 to vent the molds. These seats are formed in stepped relation and are concentric to the reservoir 13. Three flasks.v

3'. rlhe coupling' member 2 1yr-se,

formed in the coupling' member to provide l ijn seats 'ter external tapering suri'aces 85 oo at the upper of the flashs 25 and utilize the surface 33 also lor the lask 2l latter is provided with a detachable adapter having' an external tapered surface el the same ei'lective proportions as the surface and the nozzle 3l are capable ol5 relative arial movement are Islightly loose to enable the coupling` ineinber to seat tightly on the rlaslrs. This feature provides for a substantially air-tight joint between the coupling` member and one et the Jflasks when the reservoir is depressed to operative position. A sleeve el() ot iubber or other sott, elastic and non-porous material' is tiohtly bound to each of the two telescopic elements by metal ybands il to suspend the coupling` member 32, to prevent leakage between the telescopic elements and to permit the aforesaid relative axial movement.

The cylinder head 3() is bored to receive a pressuresustaining puppet valve which may be of any suitable construction. l prefer a well-known valve designed ter pneumatic tires, since it is well suited. to the requirements of my invention and may be readily applied. A valve ot' the type mentioned is indicated at l2 in Fig. 2 and shown separately by Fig. 4t. lts body is made of brass or some other sott alloy and is formed with external ribs. By boring,` the socket for its recept-ion to provide for a tight drive tit the assemblage may be simplilied. "this valve has a stein i3 which, when pressed in, releases the air or other fluid.

rlhe coupling member 32 carries valve-operating` means comprising` a screw lit. rl`his screw extends through a larger screw if and the latter is screwed into a bushing 4G having ducts Il?. rlhe bushing is driven tightly into the bore ot the coupling member. fitter the parts have been assembled the screw 4,4 is adjusted close to but not to touch the valvestem 5&3 except when the con'ipressible sleeve l() is compressed axially as hereinafter e5:- plained. rllhe shank el the screw extends through a hole in disk /lS of sheet metal which as a baille to spread the released. fluid that issues from the ducts fl The head l. ot the screw clamps the disk against the bushing 4:6.

For castings of the kind under consideration the matrix or mold is usually formed in an investment 5l of plaster which is sutli` ciently porous to permit the air to escape from the matrix as the molten metal enters the latter. As shown in Figs. 6, 7 and 8, a Crucible 52 is termed in the upper end ot the investment, and a small gate or sprue-hole 53 forms communication from the Crucible to the matrix.

lllhen themat-rix is ready to be used to make a casting the user places the necessary metal in the crucible and places the flask on its seat in the base l0. He also operates the pump 17 te charge the reservoir wits the desired pressure, say from live to fifteen pounds, according to the area of the matrix. The reservoir new occupies its upper position, as shown by l, the coupling member 52 being from one to three inches above the top otl the flask.

New, f'ith one hanl grasping the handle 1G et the reservoir7 the use? dire of a blow-torch on the metal in .nd when the instal is ituly lique' 'en f instant ot release and the development ot werking pressure in the Crucible.

'hev released fluid has merely to travel through the short ducts i7 to enter the cavity in which the molten letal is awaiting the working;- pressure. rlhe inrrshing iiuid is formed into a conical sheet by the baille plate e8, and instead et blowing; the molten metal away trom the gate or spine-hole 53 licei s a centered in the Crucible while the pressure rises. As the working pressure develops ithe crucible it 'forces the molten metal into the matrii;7 the air initially contained in the latter leaking; out through thepores of the investment. rlhe entire operation, trom the nement the reservoir is depressed, occurs in traction et a second but varies according to the area ot" the matrix.

' illhat l claim is:

l.` fin apparatus et the character described con'iprising a il sk, reservoir having a lling means carried thereby for storing fluid under pressure, said tlasl; and said reservoir being` relatively movable one toward the other to ell'ect operation and having;- mated coupling elements adapted tov toi-in a fluid-tight connection throughfwhich fluid may flew from the reservoir into the flask, a pressure-sustaining valve carried by said reservoir and normally preventing the escape of fluid through the coupling element of said reservoir, and means operable by relatively moving' the reservoir and the flask toward one anc-ther to open said valve.

2. An apparatus of the character described comprising a flask, a. reservoir having a filling means carried thereby for storing fluid under pressure, said flask and said reservoir being relatively movable one toward the other to el'leet operation, said reservoir having a dischargenozzle fixed relatively thereto, a coupling member in telescopio relation to said nozzle and movable lengthwise of its aXis, said member and said flask having mated coupling formations adapted to form a fluid-tight connection, a valve carrier by said reservoir and normally preventing the escape of fluid through said nozzle, and means operable by relative movement of said coupling member and said reservoir one toward the other to open said valve.

3. An apparatus of the character described comprising a flask, a reservoir having a filling means carried thereby for storing fluid under pressure, said ask and said reservoir being relatively movable one toward and from the other to couple them and having mated coupling element-s adapted to form a fluid-tight connect-ion through which fluid may flow from the reservoir into the flask, means to register the flask and the reservoir so that said coupling elements will go into cooperative rela' tion, a pressure-sustaining valve in the discharge end of said reservoir, and means operable by relative movement of said reservoir and flask one toward the other, while said coupling elements are coupled, to open said valve.

4. An apparatus of the character described comprising a movable reservoir for storing uid under pressure and constructed to carry yits full supply of air bodily therewith, said reservoir having a discharge nozzle fixed relatively thereto, a pressure-sustaining valve arranged in said nozzle, a coupling member surrounding and telescopically related to said nozzle to cooperate with a flask, and means operable by relative telescopic movement of said coupling member and said nozzle to open said valve.

5. An apparatus of the character described comprising a movable reservoir having a filling means carried thereby for storing fluid under pressure, means to register' a flask relatively to said reservoir, means for guiding said reservoir to and from said flask, a pressure-sustaining valve arranged in said reservoir, and coupling means carried by said reservoir to form a fluid-tight connection with the flask, said coupling means being movable relatively to said reservoir to open said valve in consequence of' beingarrested by the flask.

6. An apparatus of the character'described comprising a movable reservoir for storing fluid under pressure and constructed to carry its full supply of air bodily therewith, said lreservoir having a discharge nozzle fixed rela-tively thereto and a pressure-sustaining valve to control the discharge of fluid therethrough, a. coupling member in tele copie relation to said nozzle, resilient means arranged to form a fluidtight joint between said coupling member and said nozzle and to urge said coupling member toward the outer end of said nozzle, and means carried by said coupling member to open said valve in consequence of relative telescopic movement of said .coupling member toward the inner end of said nozzle.

7. An apparatus of the character described vcomprising a movable reservoir for storing fluid under pressure and constructed to carry its full supply of air bodily therewith, said reservoir having a discharge nozzle and a pressure-sustaining valve to control the dis charo'e of fluid therethrough, a coupling member in telescopic relation to said nozzle, a sleeve of eoi'npressible non-porous material forming a pressurestight joint between said 'nozzle and said coupling member, and means carried by said coupling member to open said valve in consequence of relatively moving said reservoir and said coupling member to compress said sleeve axially.

8. An apparatus or" the character described comprising a reservoir for fluid under pressure, a coupling member carried thereby and having a series of concentric frusto-conical surfaces arranged to make fluid-tight connection with flasks of various diameters, a support having concentric formations to reg'- ister flasks of' various diameters with said coupling member, said reservoir and said support being relatively movable one toward and from the other, guiding means to direct such relative movement, and a pressure-sustaining valve to control the discharge of fluid from said reservoir through said coupling member.

9. An apparatus of the character described comprising a movable unit, means to support and register a flask, relatively thereto, and means to guide said unit toward and from the flask, said movable unit comprising a reser- 'voir having a filling means carried thereby for storing fluid under pressure, a coupling member carried by the reservoir for supplying fluid from the reservoir to the flask, and a pressure-sustaining valve operable by said coupling member to release the fluid from the reservoir so that it may flow through said coupling member to the flask.

10. An apparatus of the character described comprising a movable unit, means to support and register a flask relatively thereto, and means to guide said unit toward and from the flask, said movable unit comprising a reservoir for storing fluid initially under pressure,

a pump for charging the reservoir with fluid, a coupling member carried by the reservo-ir for supplying fluid from the reservoir to the flask, and a pressure-sustaining valve operable by said coupling member to release the fluid from the reservoir so that it may flow through said coupling member to the flask.

1l. An apparatus of the character described Comprising a movable unit, means to support and register a' flask relatively thereto, and means to guide said unit toward and from the flask, said movable unit comprising a reservoir for storing fluid initially under pressure, a pump nested in said reservoir to charge the reservoir With fluid, said pump having an opera-ting handle outsidek the reservoir, a coupling member carried by the reservoir for supplying' fluid from the reservoir to the flask, and a pressure-sustaining valve operable by said coupling member to release the fluid from the reservoir so that it may flowT through said coupling' member to the flask.

l2. An apparatus of the character described comprising a vertically movable unit, means to guide said unit, means to register a flask relatively to said unit, and friction means to support said unit so that it may be depressed weeen manually to engage the flaslr, said unit comprising a reservoir having a lil-ling means carried thereby for storing fluid under pressure, coupling means carried thereby to supply fluid from the reservoir to the flask, and a pressuresustaining valve operable by said coupling means to release the fluid from the reservoir so that it may flow through said coupling means to the flask. Y

13. An apparatus of the character described comprising a flask, a movable reservoir for storing` fluid under pressure and constructed to carry its full supply of air bodily therewith, coupling means attached to said reservoir tosupply fluid to said flask, said coupling means and said flask having cooperative portions to form a fluid-tight connection, a valve to control the release of fluid from the reservoir to said flask, and a baffle member arranged in and secured to said coupling means to deflectthe inrushing fluid from the center toward the perimeter of the flask.

In testimony whereof I have affixed my signature this Elst day of July, 1926.

PAUL A, PITMAN 

